Posted
by
timothy
on Saturday October 30, 2010 @02:00AM
from the shine-on-harvest-moon dept.

garymortimer writes "LaserMotive (who last year won $900,000 in the NASA Power Beaming Challenge, one of the levels of the 'Space Elevator Games') have teamed up with Germany's Ascending Technologies to create an indoor flight record for electrically powered multicopters. The flight took place at the Future of Flight Aviation Center in Mukilteo, WA. LaserMotive is a Seattle-based company developing laser power beaming systems to transmit electricity without wires, for applications where wires are either cost prohibitive or physically impractical."

If you have ever played with RC helis you would realize that they have to be extremely light to even be maneuverable, let alone have any meaningful battery life. So what's interesting here is not just the rate of power transfer by laser, but that the receiving unit is light enough to support its own weight as payload in addition to keeping the heli in the air.

I'm not clear the significance of 12 hours. That's a far cry from "indefinitely" so I wonder if they just got tired of running the experiment or if

I've a few remote controlled helis. In terms of tech, they're rather pathetic compared to a housefly - which can navigate by itself, manage slight breezes, find its own fuel, even reproduce. They can fly for quite a lot longer than most battery powered RC helis.

Of course, the payload would be tiny too, milligrams I would think. And you would have to hope there was no dung or fruit trees on the way. And you need to control what they think. Nothing insurmountable, but maybe but lets stick to what can do first:-)

What I find amazing is how much better RC helicopters have become in just a few short years. In the 1980's, they cost upwards of $1000 and were incredibly difficult to learn and fly. People would spend months just learning to hover a couple feet off the ground (no exaggeration). And the radios were so prone to interference, that could crash you at any time.

Now, for $30 you can buy one that's much smaller, much lighter, yet much easier to fly (which is surprising since tiny craft are normally unstable). But the really small cheap ones fly for around 30 seconds. To fly for 12 hours isn't just a little better, it's a drastic improvement, about 100 times longer than even a hobby-quality helicopter.

That said, the FAA tends to frown on shooting powerful lasers into the sky for fear of blinding pilots. Perhaps they wouldn't worry about that in a warzone; then again usually all the aircraft above a warzone are our own.

All true, but houseflies are very bad at following orders. On the positive side, if we weaponize horseflies, given the way they like flying around the hindquarters they would be ideal for taking out troublesome government officials.

In the world of industry, made by companies few of us know exist, there exist sensors and low power chips that are powered by light sent through optical fibers.I know that's not the same thing as wireless, but I reckon for small devices, requiring small power, in environments incredibly hostile to wiring (fiber or wire), laser power+communication might be useful.

The max safe amount for a consumer laser pointer is in the 5-10mW range. Above that, serious and rather immediate damage can result from looking at it. Up in the range of 500mW they are dangerous to the point that reflected light can cause immediate eye damage. So you don't even have to look at the beam, just a specular refraction and still can get hurt. Also, this starts to get in to the "can set shit on fire" level.

Now consider that a laptop power adapter is generally in the 50-100watt range. In terms of lasers that would be "CO2 laser that blasts through steel as though it were butter."

To power anything more than a very trivial device, you'd have an unsafe level of laser power. Also it would be even worse than it sounds, because of course the receiver won't be 100% efficient.

What about multiple, simultaneous lasers in a lower power range focused on a target? Individually, the risk of harm is rather low (though I suppose there would be some area where all would come together and be dangerous), but if they're all hitting the same target...end result, I imagine (no scientist here), would be comparable at least.

It's not necessarily the most efficient solution, but where safety is concerned, it seems feasible on a basic level.

So 20,000 lasers (5mW each to generate 100watts) to power a laptop? Somehow I don't see that as at all feasible. Remember, max level for Class 3R is 5mW and that is the limit for stuff that doesn't require protective eyewear, key interlocks and so on.

Incidentally, this problem has been solved. Simply de-focus the beam at the sending end, and re-focus it at the receiver side (and do it with a diameter lens that nobody except godzilla has in their eyes - easy enough).

The goal is to spread, say 100W, in a beam that has a surface area of, say 10cm2. Since the aperture of the eye has a surface area of about 10mm2, the power delivered into the retina if someone were to glue their eyeballs to the transmitter would be 100W * 10cm2 / 10mm2 = 1W (and the eye will immediately respond by lowering that surface area to less than 1mm2, making the total delivered power less than 0.1W, and obviously, even with your retina glued to the transmitter you won't get anywhere near 10% efficiency).

Directly looking into the sun delivers about 2W to your retina (and will destroy it, but not immediately).

This is a big problem for the "solar panel in space" technologies. But it's not much of a problem really. If you were to send down 100 GW over a square kilometer, anyone could walk over the receiver perfectly safely without any protection. The power from the satellite would be a factor 1 million less than the solar irradiation (so you could send it quite safely over 10 square meters as well if needed).

1)sunlight is non-coherant
2) 5 mw =.005 W
3) 1W is 200x the limit for a "safe" laser beam, so you need at least 200x the surface area you listed
4) even.1W is 20x the safe limit, and is only reduced to that after the initial exposure of 200x, at which point the damage is already done.

Well I must admit I did the calculations rather quickly, but unless I'm radically wrong the sun's normal irradiation (that can't possibly be considered dangerous) is 1.3 kW/m2.

That means, I think, that when looking directly at the sun, at 14h noon, solar irradiation would create much more than 0.1W (about 0.2 actually). That may be uncomfortable, but we all get exposed 365 times a year.

For remote power that means that you could send 0.1W per 10 square millimeters safely. This means 100 kW per square meter.

The difference is the size of the spot on the back of your eye. Sunlight is spatially incoherent, and forms an image on the back of your eye, spreading out the light over that image. A laser is spatially coherent, so all of the light will get focused down to a very small spot, so a much higher irradiance. A (visible) 1-Watt laser will *immediately* burn a blind spot on your eye. Mid IR light is "eye safe" though, so you could withstand up to ~1 Watt (very ballpark, didn't look it up just now).

If the beam is defocused, it will spread out too rapidly to make efficient collection possible. If the beam is collimated, your eye will focus it (if its in the ~400-1200nm range). I agree that mid IR is very usable.

It does not matter what lens was used to collimate the beam in the first place. The focal length of the lens system of the eye is such that a beam with a flat wavefront (i.e., collimated) will be focused at the back of the eye.

Yes, but it will be "focused" on the entire back of the eye, not on a single spot, I hope ?

So that "focused" beam would have the same intensity on the retina as it has at the iris, no ? (or at least it would be related to aperture/retina size ratio, so unless I'm mistaken it would be weakened (as the retina is a lot bigger than the aperture, like in every camera that hopes to focus anything at all)

500mW is not dangerous. 500mW in a very small area is dangerous. For a laptop, the power receiving area could be quite large. Sunlight is approximately 1kW/m^2. Given a laptop area of about 0.05m^2 and a power consumption of 50W (100W is really high for a laptop, you'll be hard pressed to find one that uses more than 65W under full load and still counts as portable), that means that you'd need about the same amount of energy as sunlight to power it, with full efficiency.

I didn't TRFA, but last time I checked laser power systems had a transmission loss of close to 98%, which makes them somewhat impractical for laptop use. I would like wireless power, but I wouldn't like it enough to pay the electricity bill from a 2.5kW laptop.

Do you think that funny little dictator in North Korea could be suspended in air by lasers while he roasts like pig? Last night the Heat Magic basketball game seats at court side went for $25,000 per seat. I'll bet people would pay as much to watch that freak broil.

Our military contracting industry is in the business of getting more and more contracts to do useless things. They are not in the business of making useful weapons and the people paying them are not in the business of serving America's best interests.

If real private industry, or science, wanted laser-powered helicopters we'd build them at a fraction of the cost that the taxpayers are paying for this shit.

Efficient laser power systems or room-temperature superconductors are required for building a space elevator. Nothing else looks feasible for powering the climbers (you really don't want them taking fuel with them, it would add a huge amount to the energy cost).

You did not read the article then. Surprising, for a Slashdotter, I know.

If you had bothered to read the article, the Kingfisher LX-1 was designed for remote surveillance over the oceans. More impressively, power transfer is accomplished with the lasers attached to the heads of sharks. Now, if that is not an outside application, I don't know what it is........

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what is really needed is a laser powered rocket. you shine the lasers on a heat exchanger on the rocket, through which hydrogen is pumped, and the superheated hydrogen is blasted out the back. i believe it has the specific impulse for a single stage to orbit vehicle

So if these laser pointers can do so much damage/destruction to pilots/planes... does this mean that a bunch of terrorists with cheap lasers can wreak havoc . . . ? Or did we just let the cat out of the bag . . . ?

Any military/commercial pilots out there? Are there any protective measures . . . ?

Any asshole pointing a laser at an airplane, should be tossed into a pool full of sharks.

You are using bureaucratic rule to limit the advancement of technology. You must work for the government.

No, he's not. Using technology to harm and potentially kill people will remain illegal no matter how advanced the technology gets. Those sort of rules don't limit technology itself, just how it is applied.

Sorry, thought you were replying directly to the news story about lasers. I really hate this new post display system since in this case, there was no indication that there was a post between the original post and yours.

Could make it easier to make a Single Stage to Orbit Ion-Plasma rocket. Just have a power plant on the surface and then one in orbit and when the rocket gets 1/2 way into space switch to the space based power source. Smaller more powerful rockets and cheaper access to space.